Install box2d using conda, not pip

environment.yml

@@ -3,6 +3,7 @@ channels:
   - conda-forge
   - defaults
 dependencies:
+  - box2d-py  # used only in chapter 17, exercise 8
   - ftfy=6.0  # used only in chapter 15 by the transformers library
   - graphviz  # used only in chapter 5 for dot files
   - gym=0.19  # used only in chapter 17
@@ -44,7 +45,7 @@ dependencies:
     - tfx~=1.3.0  # platform to deploy production ML pipelines
     - transformers~=4.11.3  # Natural Language Processing lib for TF or PyTorch
     - urlextract~=1.4.0  # optionally used in chapter 3, exercise 4
-    - gym[box2d,atari,accept-rom-license]~=0.21.0  # used only in chapter 18
+    - gym[atari,accept-rom-license]~=0.21.0  # used only in chapter 18
 
 # Specific lib versions to avoid conflicts
   - attrs=20.3